Influence of Moringa oleifera gum on two polymorphs synthesis of MnO2 and evaluation of the pseudo-capacitance activity

This work reports the preparation of two polymorphs of MnO2 such as α-MnO2 and β-MnO2 by simple microwave method using natural Moringa oleifera gum. The concentration of M. oleifera gum solution influences the formation of α-MnO2 and β-MnO2, and the structural formation of the metal oxides was confirmed by powder X-ray diffraction analysis. According to the surface analysis of the prepared materials studied through scanning electron microscopy and transmission electron microscopy, nanocacti α-MnO2 and rice husk shaped β-MnO2 nanorod morphology were observed. The fabricated α-MnO2 and β-MnO2 electrode materials on Ni foam showed good electrochemical behaviours in the cyclic voltammogram using a three-electrode system and exhibited a specific capacitance of 150 Fg−1 and 92.8 Fg−1 at a current density of 0.5 Ag−1 in the galvanic charge–discharge studies, respectively. Furthermore, cycling stability study of the α-MnO2 material showed capacitance retention of 95.4% at a current density of 6 Ag−1 after 2000 galvanostatic charge–discharge cycles.